This invention relates generally to ring laser gyroscopes (gyros) and particularly to a ring laser gyro arranged for supporting plasma excitation and optical gain transverse to rather than parallel with the optical axis of the gyro.
Ring laser gyros generally feature a base of a ceramic material having a low coefficient of thermal expansion and passageways within the base which, together with mirrors, form a closed optical cavity for counterpropagating beams of coherent light. The base forms a sealed envelope containing a suitable gas under a low pressure in the closed optical cavity. Electrodes (two anodes and a common cathode) are disposed in communication with the optical cavity so that an electrical potential sufficient to support plasma excitation and lasing is maintained in the gas. As is well known in the ring laser gyro art, the laser has a gain section which is that portion of the closed optical cavity in which the electrodes, when energized, maintain a discharge in the ionized gas or plasma.
In conventional arrangements, this discharge is in a direction parallel to the optical axis of the gyro. It has been found that in these arrangements gas flow bias errors are introduced into the gyro. Also, the gas volume within the closed optical cavity is limited; movement of the gas atoms in the optical cavity requires substantially equal currents through the two anodes; and there is a distinct tendency for gas flow oscillations at high current values.
The arrangement of the present invention tends to avoid these disadvantages by permitting the gas atoms to flow in a direction transverse to the optical axis, whereby the aforenoted gas flow bias error is minimized.
The transverse discharge arrangement has particular applicability to small gyros where discharge space is at a premium in that increased gas volume is offered which increases gyro operating and storage life as will now be recognized.